diff --git a/kmod/src/data.c b/kmod/src/data.c
index bf934084..6b581a3b 100644
--- a/kmod/src/data.c
+++ b/kmod/src/data.c
@@ -456,11 +456,13 @@ static int alloc_block(struct super_block *sb, struct inode *inode,
 
 	} else {
 		/*
-		 * Preallocation of aligned regions only preallocates if
-		 * the aligned region contains no extents at all.  This
-		 * could be fooled by offline sparse extents but we
-		 * don't want to iterate over all offline extents in the
-		 * aligned region.
+		 * Preallocation within aligned regions tries to
+		 * allocate an extent to fill the hole in the region
+		 * that contains iblock.  We search for a next extent
+		 * from the start of the region.  If it's at the start
+		 * we might have to search again to find an existing
+		 * extent at the end of the region.  (This next could be
+		 * given to us by the caller).
 		 */
 		div64_u64_rem(iblock, opts.data_prealloc_blocks, &rem);
 		start = iblock - rem;
@@ -468,8 +470,20 @@ static int alloc_block(struct super_block *sb, struct inode *inode,
 		ret = scoutfs_ext_next(sb, &data_ext_ops, &args, start, 1, &found);
 		if (ret < 0 && ret != -ENOENT)
 			goto out;
-		if (found.len && found.start < start + count)
-			count = 1;
+
+		/* trim count if there's an extent in the region before iblock */
+		if (found.len && found.start < iblock) {
+			count -= (found.start + found.len) - start;
+			start = found.start + found.len;
+			/* see if there's also an extent after iblock */
+			ret = scoutfs_ext_next(sb, &data_ext_ops, &args, iblock, 1, &found);
+			if (ret < 0 && ret != -ENOENT)
+				goto out;
+		}
+
+		/* trim count by a next extent in the region */
+		if (found.len && found.start > start && found.start < start + count)
+			count = (found.start - start);
 	}
 
 	/* overall prealloc limit */
@@ -1253,6 +1267,7 @@ int scoutfs_data_move_blocks(struct inode *from, u64 from_off,
 	from_iblock = from_off >> SCOUTFS_BLOCK_SM_SHIFT;
 	count = (byte_len + SCOUTFS_BLOCK_SM_MASK) >> SCOUTFS_BLOCK_SM_SHIFT;
 	to_iblock = to_off >> SCOUTFS_BLOCK_SM_SHIFT;
+	from_start = from_iblock;
 
 	/* only move extent blocks inside i_size, careful not to wrap */
 	from_size = i_size_read(from);
@@ -1329,7 +1344,7 @@ int scoutfs_data_move_blocks(struct inode *from, u64 from_off,
 
 			/* find the next extent to move */
 			ret = scoutfs_ext_next(sb, &data_ext_ops, &from_args,
-					       from_iblock, 1, &ext);
+					       from_start, 1, &ext);
 			if (ret < 0) {
 				if (ret == -ENOENT) {
 					done = true;
@@ -1417,6 +1432,12 @@ int scoutfs_data_move_blocks(struct inode *from, u64 from_off,
 							i_size_read(from);
 				i_size_write(to, to_size);
 			}
+
+			/* find next after moved extent, avoiding wrapping */
+			if (from_start + len < from_start)
+				from_start = from_iblock + count + 1;
+			else
+				from_start += len;
 		}
 
 
diff --git a/tests/golden/data-prealloc b/tests/golden/data-prealloc
index 93854034..f6ac8d65 100644
--- a/tests/golden/data-prealloc
+++ b/tests/golden/data-prealloc
@@ -24,3 +24,325 @@
 /mnt/test/test/data-prealloc/file-2: 5 extents found
 /mnt/test/test/data-prealloc/file-1: 3 extents found
 /mnt/test/test/data-prealloc/file-2: 3 extents found
+== block writes into region allocs hole
+wrote blk 24
+wrote blk 32
+wrote blk 40
+wrote blk 55
+wrote blk 63
+wrote blk 71
+wrote blk 72
+wrote blk 79
+wrote blk 80
+wrote blk 87
+wrote blk 88
+wrote blk 95
+before:
+24.. 1: 
+32.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 0 at pos 0
+wrote blk 0
+0.. 1: 
+1.. 7: unwritten
+24.. 1: 
+32.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 0 at pos 1
+wrote blk 15
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+24.. 1: 
+32.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 0 at pos 2
+wrote blk 19
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+32.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 1 at pos 0
+wrote blk 25
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 1 at pos 1
+wrote blk 39
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 1 at pos 2
+wrote blk 44
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 2 at pos 0
+wrote blk 48
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 2 at pos 1
+wrote blk 62
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+56.. 6: unwritten
+62.. 1: 
+63.. 1: 
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 2 at pos 2
+wrote blk 67
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+56.. 6: unwritten
+62.. 1: 
+63.. 1: 
+64.. 3: unwritten
+67.. 1: 
+68.. 3: unwritten
+71.. 2: 
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 3 at pos 0
+wrote blk 73
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+56.. 6: unwritten
+62.. 1: 
+63.. 1: 
+64.. 3: unwritten
+67.. 1: 
+68.. 3: unwritten
+71.. 2: 
+73.. 1: 
+74.. 5: unwritten
+79.. 2: 
+87.. 2: 
+95.. 1: eof
+writing into existing 3 at pos 1
+wrote blk 86
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+56.. 6: unwritten
+62.. 1: 
+63.. 1: 
+64.. 3: unwritten
+67.. 1: 
+68.. 3: unwritten
+71.. 2: 
+73.. 1: 
+74.. 5: unwritten
+79.. 2: 
+81.. 5: unwritten
+86.. 1: 
+87.. 2: 
+95.. 1: eof
+writing into existing 3 at pos 2
+wrote blk 92
+0.. 1: 
+1.. 14: unwritten
+15.. 1: 
+16.. 3: unwritten
+19.. 1: 
+20.. 4: unwritten
+24.. 1: 
+25.. 1: 
+26.. 6: unwritten
+32.. 1: 
+33.. 6: unwritten
+39.. 1: 
+40.. 1: 
+41.. 3: unwritten
+44.. 1: 
+45.. 3: unwritten
+48.. 1: 
+49.. 6: unwritten
+55.. 1: 
+56.. 6: unwritten
+62.. 1: 
+63.. 1: 
+64.. 3: unwritten
+67.. 1: 
+68.. 3: unwritten
+71.. 2: 
+73.. 1: 
+74.. 5: unwritten
+79.. 2: 
+81.. 5: unwritten
+86.. 1: 
+87.. 2: 
+89.. 3: unwritten
+92.. 1: 
+93.. 2: unwritten
+95.. 1: eof
diff --git a/tests/tests/data-prealloc.sh b/tests/tests/data-prealloc.sh
index b0bb81d2..09f42637 100644
--- a/tests/tests/data-prealloc.sh
+++ b/tests/tests/data-prealloc.sh
@@ -6,6 +6,15 @@
 #
 t_require_commands scoutfs stat filefrag dd touch truncate
 
+write_block()
+{
+	local file="$1"
+	local blk="$2"
+
+	dd if=/dev/zero of="$file" bs=4096 seek=$blk count=1 conv=notrunc status=none
+	echo "wrote blk $blk"
+}
+
 write_forwards()
 {
 	local prefix="$1"
@@ -70,6 +79,25 @@ print_extents_found()
 	filefrag "$prefix"* 2>&1 | grep "extent.*found" | t_filter_fs
 }
 
+#
+# print the logical start, len, and flags if they're there.
+#
+print_logical_extents()
+{
+	local file="$1"
+
+	filefrag -v -b4096 "$file" 2>&1 | t_filter_fs | awk '
+		($1 ~ /[0-9]+:/) {
+			if ($NF !~  /[0-9]+:/) {
+				flags=$NF
+			} else {
+				flags=""
+			}
+			print $2, $6, flags
+		}
+	'
+}
+
 t_save_all_sysfs_mount_options data_prealloc_blocks
 t_save_all_sysfs_mount_options data_prealloc_contig_only
 restore_options()
@@ -133,4 +161,70 @@ t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
 write_forwards $prefix 3
 print_extents_found $prefix
 
+#
+# prepare aligned regions of 8 blocks that we'll write into.
+# We'll right into the first, last, and middle block of each
+# region which was prepared with no existing extents, one at
+# the start, and one at the end.
+#
+# Let's keep this last because it creates a ton of output to read
+# through.
+#
+echo "== block writes into region allocs hole" 
+t_set_sysfs_mount_option 0 data_prealloc_blocks 8
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 1
+touch "$prefix"
+truncate -s 0 "$prefix"
+
+# write initial blocks in regions
+base=0
+for sides in 0 1 2 3; do
+	for i in 0 1 2; do
+                case "$sides" in
+			# none
+			0) ;;
+			# left
+			1) write_block $prefix $((base + 0)) ;;
+			# right
+			2) write_block $prefix $((base + 7)) ;;
+			# both
+			3) write_block $prefix $((base + 0)) 
+			   write_block $prefix $((base + 7)) ;;
+		esac
+		((base+=8))
+	done
+done
+
+echo before:
+print_logical_extents "$prefix"
+
+# now write into the first, middle, and last empty block of each
+t_set_sysfs_mount_option 0 data_prealloc_contig_only 0
+base=0
+for sides in 0 1 2 3; do
+	for i in 0 1 2; do
+		echo "writing into existing $sides at pos $i"
+		case "$sides" in
+			# none
+			0) left=$base; right=$((base + 7));;
+			# left
+			1) left=$((base + 1)); right=$((base + 7));;
+			# right
+			2) left=$((base)); right=$((base + 6));;
+			# both
+			3) left=$((base + 1)); right=$((base + 6));;
+		esac
+		case "$i" in
+			# start
+			0) write_block $prefix $left ;;
+			# end
+			1) write_block $prefix $right ;;
+			# mid (both has 6 blocks internally)
+			2) write_block $prefix $((left + 3)) ;;
+		esac
+		print_logical_extents "$prefix"
+		((base+=8))
+	done
+done
+
 t_pass